Читать книгу The Rheology Handbook - Thomas Mezger - Страница 240

As long as under a constantly acting constant stress, ideal-viscous fluids are showing continuously increasing deformation. After removing the load, there is no re-formation at all since this kind of material does not have any elastic proportion (see Figure 6.4). Ideal-viscous fluids are not able to store any deformation energy during the stress interval, and therefore after releasing the load, they finally remain deformed to the same extent as they showed in the end of the stress phase.

Here, the following applies for the ratio of the finally occurring deformation values:

γv = γmax and γe = 0 (see Figure 6.2).

Figure 6.3: “Creep curve” of an ideal-elastic

solid (inverted commas, since in the stress phase there is no creep at all), and creep recovery curve (in the rest phase there is an immediate recovery step in deformation, back to zero)

Figure 6.4: Creep curve and “recovery curve” of an ideal-viscous fluid (inverted commas, since in the rest phase there is no recovery of deformation at all)

Figure 6.5: Creep and creep recovery curves of two different viscoelastic materials, in the rest phase both are showing delayed re-formation:

(1) only partially for the VE liquid, and

(2) finally completely for the VE solid